1. Field of the Invention
The present invention generally relates to optoelectronic integrated circuits, and more specifically to a manufacturing method for optoelectronic integrated circuits including a photo diode formed on a semiconductor substrate, which transforms light into electric signals, a hetero bipolar junction transistor (hereinafter abbreviated as HBT) which amplifies the electric signals outputted from the photo diode, a capacitor which by-passes electric signals and a resistor which drops the voltage of a received signal, wherein the capacitor and the resistor are passive devices.
2. Description of the Related Art
An optoelectronic integrated circuit, used as an optical receiver in high frequency optical communication systems, generally includes a photo diode which transforms light produced from a light emitting diode into electric signals, an HBT which amplifies the electric signals produced from the photo diodes, and capacitors, resistors, etc.
A manufacturing method for a conventional optoelectronic diode as mentioned above is given below with reference to FIG. 1.
An HBT (h) which includes an emitter, a base, and a collector, and a photo diode(p), which includes a P type electrode and an N type electrode, are formed on selected portions of a semiconductor substrate 101 by a conventional method. The HBT(h) and the photo diode(p) are electrically isolated from each other. Thereafter, a first insulation film 102, for example, a SiO.sub.2 film or a SiN film is deposited over the photo diode(p) and the HBT(h) to protect the same.
Afterwards, pad metal patterns 103, 104 are formed on the first insulating film of both sides of the HBT(h) and the photo diode(p) respectively utilizing the conventional lift off method. In the above process, a lower electrode 105 for a capacitor is also formed on the first insulation film 102. The lower electrode 105 is adjacent to the photo diode(p), and is separated by a selected distance from the photo diode(p).
A second insulation film 106, a dielectric film for the capacitor, for example a SiN film, is deposited over the above described resulting structure. The second insulation film 106 is then etched so that it exists only on top of the lower electrode 105. Afterwards, an upper electrode 107 is formed on top of the lower electrode 105 using a conventional method so as to form a capacitor. Continuously, a resistor 108 is formed using a metal film, such as NiCr, on one side (on a different side with respect to the photo diode(p)) of the capacitor.
Afterwards, predetermined parts of the first insulation film 102 are etched so that the emitter electrode of the HBT(h) and the electrodes of the photo diode(p) are exposed. Next, metal wiring 109, 110 are formed. The metal wiring 109 electrically connects the exposed emitter electrode with the pad metal pattern 103 and the metal wiring 110 electrically connects the exposed electrodes of the photo diode(p) with the pad metal pattern 104.
Afterwards, in certain circumstances, the first insulation layer 102 located on top of the photo diode(p), i.e., the optical receiver, is removed. Then a third insulation film(112), such as a SiN film, is formed to reduce the reflective ratio of induced light.
However, the above described conventional method of manufacturing the optoelectronic integrated circuit technology causes problems such as follows.
After the photo diode(p) and the HBT(h) are formed, the steps of forming the protective first insulation film(102), the dielectric second insulation film(106), and the anti-reflective third insulation film(112) are performed. Although the above described insulation films are of similar materials, the number of steps required to form the insulation layers are increased.
Moreover, to form the above described insulation layers in the appropriate locations, three patterning steps are necessary.
The above mentioned problems cause increases in manufacturing time and cost.